1st LO unlock indicates a hardware problem. The instrument will need to be repaired.
Contact Telonic for service on this instrument.
Calibration interval for the DSA800 family is 1 year. Most RIGOL instruments specify a 1 year interval. Some instruments specfication document have specifications for multiple intervals.
On any specification document you can find the interval for the instrument.
To learn more about using RIGOL Instruments in EMC Precompliance testing go to our application site at:
www.rigolemc.com
To learn more about using RIGOL Instruments in EMC Precompliance testing go to our application site at:
www.rigolemc.com
1. Measuring the performance of a crystal filter
Hams use crystal filters in their radios to enhance selectivity, but short of installing the
filter there is really no easy way to test one. A spectrum analyser with a tracking generator
makes it fairly easy. Simply feed the tracking generator into the filter input and look at the
resulting response from the filter output.
A nice additional feature on some spectrum analysers is the “N dB” feature that makes it
easy to find the point where the response is N dB down from that at the filter center
frequency.
2. Testing and adjusting duplexers and diplexers
Duplexers are used in repeater installations to allow a single antenna to be used for
simultaneous receive and transmit on slightly separated frequencies. In order to do this the
duplexer has to be adjusted so that it provides the required attenuation of the transmitter
frequency so that it does not interfere with the receiver.
Any repeater owner has to deal with tuning a duplexer at some point. A spectrum analyser
with a tracking generator makes this easy.
A diplexer allows the use of a single antenna on two different bands, and is a lot smaller
than a duplexer. Lots of HAMs use diplexers in their cars to allow a single antenna to be
used on both the VHF and UHF bands.
3. Coaxial stub tuning and coaxial cable measurements
Attach a piece of coaxial cable to the input/output of the tracking generator using
a T connector. First, this shows you the frequency where the cable is 1/4
wavelength long. ¼ wavelength coaxial stubs are often used to reduce interference from
nearby transmitters. You can trim a piece of coaxial cable until you reach the frequency
you want just by cutting a small amount from the cable and watching the response on the
screen.
Another useful feature using the T-connector technique is that when you have determined
the frequency where the cable is 1/4 wavelength long you can easily determine the
physical length of the cable without actually having to measure it. All you need to know is
the frequency where the cable is 1/4 wavelength long (read from the screen on the
spec an) and the velocity factor of the cable which is a specification that can be looked up
for any type of cable.
Then the length of the cable (in feet) is calculated by the formula L = (246*Vf) / F, where
F is the frequency in MHz.
4. Antenna performance (return loss)
The return loss of an antenna is a measure of how close its impedance is to that of the
system driving it. You can measure return loss with the spectrum analyser and the tracking
generator if you have a directional coupler. By attaching the reflected port to the spectrum
analyser you can measure the return loss of an attached antenna, and you can calculate
VSWR from return loss by the formula VSWR = (1+(10^RL/20)) / ((10^RL/20)-1) where
RL is the measured return loss.
5. FM and AM Radio Channel performance.. you can demodulate, see the frequency and
amplitude deviation, etc..
The Rigol DSA-815 Spectrum Analyser represents a significant shift in how companies perform EMI and EMC testing. Now, R&D Engineers can afford to have test equipment that allows them to troubleshoot and test designs on their bench without having to schedule and pay for time at a full compliance lab.
As with any product, there are trade-offs for cost vs. performance. The DSA-815 is a great tool and provides many useful features for the price, but it does not perform exactly like fully compliant EMC test instruments.
The following list highlights some of the key requirements of CISPR 16-1-1 and where the DSA-815 meets or deviates from those.
Full compliance to CISPR 16-1-1 requires the EMI test receiver is of at least the following performance:
1. Frequency range: 9 kHz – 1000 MHz
DSA-815 frequency range: 9kHz to 1500MHz
2. Amplitude accuracy ±2 dB absolute amplitude accuracy
DSA-815 absolute amplitude accuracy < 2dB
3. The frequency response of the filters must also fall within a “mask” defined by CISPR 16.
The EMI filters in DSA800 are designed according to CISPR16.
4. CISPR Specified detectors are Peak, quasi-peak, and average and the charge, discharge time and meter constants of the quasi-peak detector are specified.
DSA800 has been designed to achieve CISPR performance , but has not been tested at this time
5. Specified input impedance must have a nominal value of 50 ohms with deviations specified: With 0dB attenuation: VSWR should less than 2, and with 10dB attenuation, VSWR should less than 1.2
The VSWR of DSA1000 and DSA815 have VSWR’s of about 1.5
6. Pass product immunity in a 3 V/m field
The DSA -815 has not been tested at this time.
7. CISPR “Pulse Test”/Preselection: Preselection is achieved by input filters that track the receiver tuning to reduce broadband noise overload at the front end mixer.
There is no preselection in DSA-815.
8. CISPR “Pulse Test”/Sensitivity and dynamic range. The EMI receiver must have a noise floor low enough to measure signals at low Pulse
Repetition Frequencies (PRFs)
The DSA-815 has been tested to these values as of late 2013. Contact Rigol (see below) for CISPR 16 Calibration Report.
9. Intermediate frequency rejection ratio and Image rejection ratio should be greater than 40dB.
The DSA-815 spec is about 60dBc.
RIGOL Spectrum Analysers are utilized in many applications, but EMC PreCompliance is of particular interest to our customers. All our applications content related to EMC can be found at:
www.rigolemc.com
Here are some additional details about the DSA-815 series of spectrum analysers:
1) What is the output impedance for the earphone?
• Typically around 100 OHM (non-specified)
2) What is the output power of earphone?
• 10mW Output Power. But it is not guaranteed.
3) Is the earphone stereo or mono?
• mono
4) Is the demodulation stereo or mono?
• mono
5) What type of earphone jack?
• 3.5mm
The Rigol DSA1000 and DSA800 series spectrum analysers have demodulation capabilities.
Here are some hints that can optimize the demodulation output.
1. Use an antenna matched for the frequencies of interest
2. Set the center frequency of the spectrum analyser to the center frequency of the signal of interest. For example, of you wish to demodulate an FM signal with a carrier of 100MHz, set your spectrum analyser center frequency to 100MHz.
3. Select the proper demodulation type (AM for AM signals, FM for FM)
4. Enable the earphone or speaker on the spectrum analyser
5. Insert a 3.5mm stereo or mono earphone set into the 3.5mm headphone jack (DSA815)
6. Set the demodulation time to 1s
7. Set the RBW to 1MHz
8. Adjust the volume to a safe level. You can also tweak RBW to lock in signal.
Here is a user submitted application note on measuring Digital TV Pilot Carrier frequency.
Thanks to Frank Hertel Newman-Kees RF Measurements & Engineering.
1. Under Control — “BW / Det” — “Det Type”, select POS PEAK Detector.
2. Under Control — “Trace / P/F” — “Trace Type”, select CLEAR / WRITE.
3. Under Marker — “Marker”, select NORMAL.
4. Under Marker — “Marker Fctn”, select “Frequency Count”
5. Under “State” Select ON — Then Select “Resolution” and set it to 1 HZ / MANUAL
6. Under Control — “TG” Assure that “TG” is OFF
7. Under Control — “Sweep / Trig” Select “Time / Manual”
8. Set the “Sweep/Time” between 0.16 seconds and .60 seconds . Other SWEEP times can be used for desired and best results.
9. Under Control — “BW / Det” Set RBW to Manual & 100 Hz
10. Under Control — Set VBW to Manual & 1 KHz
11. Under Span — Set SPAN to 3 KhzSo you will be able to see the “Pilot Carrier”, in case the station is “Off Frequency / Out of limits”)
12. Under Freq — Enter the TV Channel’s Pilot FREQUENCY I.E. xxx,309,441 Hz
13. Once you can see the “Pilot Carrier”, centered in the display, you can then narrow the “Span” to between 1,000 Hz and 500 Hz and set “VBW” to 10 HZ
14. Under Marker — “Peak”, set “Cont Peak” to “ON”
15. Read the Channel’s “Pilot Carrier” FREQUENCY (with 1 HZ Resolution) as displayed in the upper Right area of the screen
16. For a more Precise Frequency Measurement, you will need to connect a “Precision” 10 Mhz Reference Signal to the rear “10 Mhz In “, BNC connector
NOTE: For Antenna / Distant Measurements:
Set Reference level (Ampt – “Ref Level” at –20 to –30 DBM)
Set “Input Atten” at 10 DB / MANUAL
Set “Pre-Amp” ON
Set “Input” 75 Ω